The present invention relates generally to event sensing and more particularly to an electronic circuit for sensing when a moving part driven by electromotive force has abruptly or discontinuously changed movement characterized by a substantially instantaneous change in velocity. The invention is thus useful for sensing when valve seating has occurred in a solenoid operated electromechanical valve.
It is often difficult to electrically determine when a moving mechanical part within a piece of machinery has reached a given location or displacement. In an electromechanical valve, for instance, the precise location of the valve is often difficult to determine, because the valve may be located in a fluid sealed system and cannot be easily outfitted with attached position sensors or contact sensors. In a fluid sealed system, it is difficult to convey signals from an attached sensor to external electronic equipment, since the signal wires or other telemetry path must cross the fluid seal boundary creating a problem with leaks.
Magnetic sensors, in which a magnet is placed on the valve and a remotely located magnetic field senses position, may work in some applications. However, magnetic sensors are not universally useful since metal valve bodies and housings can block magnetic fields, rendering such sensors ineffective. Optical sensors have similar problems.
The present invention solves the sensing problem in a simple, yet elegant manner. Rather than relying on attached sensors and remote telemetry paths, the invention monitors the waveforms of the electrical energy being supplied the electromotive device. By sensing the time rate of change in the voltage across the electromotive device a transition is detected when a discontinuity occurs in the accelleration of the moving part. This voltage time rate of change is detected and used to determine the time at which the accelleration discontinuity occurred. From this information part position or displacement may be determined. In an electromechanical valve, this information may be used to determine when valve seating occurs.
For a more complete understanding of the invention, its objects and advantages, reference may be had to the following specification and to the accompanying drawings.